It is often desired to ascertain the flow pattern of water through porous underground formations such as ore bodies from which metals are extracted by solution mining processes. Methods for tracing the flow of water are many and varied, e.g. U.S. Pat. No. 2,868,625 teaches a method for tracing the flow of water by the incorporation of a small amount of a compound such as ethylenediaminetetraacetic acid into injection water and testing the water removed from a product well located at a point distant from the point of injection for such compound. This method makes it possible to follow the arrival of the injection water at several production wells from the injection well. However, the path of such water will not be detectable merely by analyzing the water at the production well. This method will only determine that the water is moved in some pathway from said injection well to the production well.
In U.S. Pat. No. 3,508,875 a different tracer is added to three different injection wells and the outflow from the production well is analyzed to determine the presence of each individual tracer. This method again allows the operator to determine whether the water is moving between any or all injection wells and the production well, however the exact flow path of the water is not known.
Other methods for tracing the flow of underground water include providing fluorescent dyes in water soluble form in said water and measuring the fluorescence of the outflow well.
None of these methods solve one of the basic problems found in `in situ` solution mining processes. As used throughout this specification, the term `in situ` solution mining refers to a process wherein an extraction solution is injected into the ground through one or more injection wells to contact a subterranean deposit of an ore, and a solution containing metal values dissolved from said ore is recovered from one or more production wells. In `in situ` solution mining processes it is desirable to know whether the solution has been in contact with all of the ore. `In situ` solution mining processes are disclosed generally in U.S. Pat. Nos. 3,910,636; 3,647,261; 3,574,599; 3,215,471; and 3,853,353. None of these patents discuss methods for insuring that all of the ore is contacted with the extraction solution. It is, however, known in the art that when extracting copper from feldspar ores, wherein an oxidizing agent is added to the sulfuric acid extraction solution, that the residue of the extracted feldspar contains ferric hydroxide. Samples may be taken by coring into the ore to determine whether ferric hydroxide is present. In locations where ferric hydroxide is found it is presumed that the leaching solution has been in contact with the ore. This method, however, does not rely on providing a material that will react with the extracted ore nor is this method suitable for ores containing low amounts of iron in association with the copper, e.g. oxide type ores chrysocolla. It is thus an object of the invention to provide a method for determining whether such copper oxide-type ores have been in contact with the copper extraction solution. Other objects of the instant invention will be obvious from the below specification.